I maybe wrong but a 'clicking' HD usually means that that part of ur drive is dead. Bad sectors!
When it 'clicks' does ur PC 'hang' aswell, then crash?
Its because windows is trying to run something that is installed over the bad sectors.
Defragging ur drive will cure it as a temp measure cos windows will move any files away from the bad sectors but when u install something else u'll probably do it over the bad sectors again and the problem will return!
My advice would be to backup and get a new HD before u loose something important.
Or get a new drive and use this one as a slave to and transfer everything across.